Enhanced Seedling Growth Research Articles

Changes in Nutrient-Homeostasis and Reserves Metabolism During Rice Seed Priming: Consequences for Seedling Emergence and Growth

In this study influence of different seed priming treatments on the nutrient-homeostasis and reserve metabolism during seedling emergence and growth of rice were determined. Seed priming treatments included pre-germination, hydropriming for 48 h, osmohardening with KCl and CaCl 2, ascorbate priming and hardening. All treatments shortened the emergence time and enhanced the energy and index of seedling emergence. Seedlings from primed seeds had greater length, number of roots and fresh and dry mass than control. Among the treatments, CaCl 2, ascorbate and KCl proved better in enhancing emergence and seedling growth. Seed priming changed the pattern of N and Ca 2+ homeostasis both of the seeds and seedlings, which were associated to enhancing α-amylase activity and reducing sugars content. Positive correlations of seedling attributes with nutrient content suggested that as a result of seed priming, most of N and Ca 2+ were partitioned to embryo, which enhanced seedling emergence and subsequent growth of rice seedlings.

Bio-inoculant formulations for enhanced seedling emergence and pasture growth

Soil-borne damping-off diseases are a major constraint limiting pasture seedling emergence and yield. Large scale laboratory and glasshouse screening of beneficial micro-organisms against several host/pathogen systems was conducted to identify efficient bio-control and growthpromoting microbes. This was followed by field-testing of the best microbes and their formulations for efficient application techniques. The research identified a number of fungal (Trichoderma spp.) and bacterial (Paenibacillus spp.) isolates which suppressed damping-off diseases and promoted plant growth of various pasture species. Preliminary field-trials with granule and seed-coat formulations confirmed the glasshouse results. Intensive research trials with a mix of four T. atroviride isolates, providing growth promotion and disease control activity, led to the development of a prototype pasture seed additive product. Keywords: damping-off diseases, Paenibacillus spp., seed-coating, Trichoderma spp.

Influence of elaiosome on postdispersal dynamics of an ant-dispersed plant

Specialized myrmecochorous plants bear an elaiosome attached to the seed. Ants benefit from food provided by this appendage and plants get their seeds eventually dispersed. Aside from the benefits conferred by seed dispersal, we hypothesize that the influence of the elaiosome might extend to later life history stages such as emergence or survival, but few studies have examined rigorously such delayed effects on seed and seedling dynamics. This paper tests this hypothesis for the ant-dispersed herb Helleborus foetidus. Presence or lack of the elaiosome had some interesting delayed influences. Specifically, our results show that elaiosome removal not only enhanced seedling emergence, but also reduced cumulative long-term seed predation. The combination of these two effects, together with the inherent positive effect of the elaiosome on seed dispersal, highlights the ecological and evolutionary importance of myrmecochorous systems.

Effects of Pre-sowing Seed Treatments on Tomato (Lycopersicon esculentum (L.) Mill) Seedling Emergence

The effects of pre-sowing seed treatments with the bioregulators, Indole - acetic acid (IAA), Indole butyric acid (IBA) and Naphthalene acetic acid (NAA) on seedling emergence of tomato (Lycopersicon esculentum (L.) Mill, genotypes NHLy 11, NHLy 12, NHLy 13, NHLy 15 and NHLy 16 were investigated. The treatments consisted of soaking in 25mg/L, 50mg/L, 75mg/L, 100mg/L, 125mg/L and 150mg/L concentrations of each of the bioregulators and control replicated three times in a completely randomised design. Results showed that seedling emergence was enhanced by all bioregulator treatments at 100mg/L relative to control, the highest values being 92.1, 88.4 and 89.4% for the IAA, IBA and NAA treatments respectively. Marked reduction of seedling emergence was recorded at higher concentrations of 125 and 150mg/L for all test genotypes. This work showed that pre-sowing seed treatments with the bioregulators used in this work are effective in enhancing seedling emergence of tomato, especially at 100mg/L concentration.

Seed quality effects on seedling emergence, plant stand establishment and grain yield in two-row barley

Seed viability and vigour play important roles in seedling emergence, plant stand establishment and yield potential. The majority of cereal fields in Finland are typically sown with farm saved seed (FSS). If the quality of the seed is not known, there can be insidious yield reduction. This research was conducted to study the effects of seed quality on seedling emergence rate, seedling number and yielding capacity. The study comprised three-year field experiments conducted during 2007–2009, established at three sites: Jokioinen, Nousiainen and Ylistaro. Spring barley cultivars Saana (2007) and Annabell (2008-2009) were sown at rate of 500 germinating seeds m-2. Five seed lots were included as treatments: farm saved seed (FSS); downgraded seed 2.7 mm); upgraded seed >2.7 mm with disinfection (FSS>2.7 mm + dis); and commercial certified seed with disinfection (CCS). Up- and down-graded seed lots (FSS2.7 mm, and FSS>2.7 mm + dis) all originated from the FSS. Seedling emergence rate was measured from the time when coleoptiles started to break through the soil surface. The number of seedlings (3 × 1 m row per plot) was recorded at five-day intervals four times from the same rows. Plots were harvested at physiological maturity and grain yield (kg ha-1), hectolitre weight (HLW, kg) single grain weight (SGW, mg) and grain protein content (%) were recorded. Seed lots of CCS and FSS>2.7 mm + dis enhanced seedling emergence rate and increased the number of plants compared with other treatments. These two seed lots also produced the highest grain yield and had the lowest grain protein. Seed quality had an apparent effect on plant stand establishment and grain yield. A seed lot effect was evident despite identical targeted sowing rates that took into account germination rate and seed weight. Therefore, differences in seedling emergence and yielding capacity were likely outcomes of variation in seed vigour among the five treatments.;

Effects of plant growth regulators on growth and carbohydrate accumulation in shoots and roots of two almond rootstock seedlings

Introduction. Prunus amygdalus and P. webbii can be used as rootstocks for almond cultivars due to their adaptability to severe environmental conditions. However, the time required for seedlings to reach a suitable size for transplanting may take 1 to 3 years. Our study tested the effects of foliar application of growth regulators on the vegetative growth and carbohydrate accumulation in shoots and roots of these species. Materials and methods. Six-week-old seedlings were treated with gibberellic acid (GA3) (100 mg·L–1) alone or with GA3 followed by ethephon [(100 and 200) mg·L–1], or chlormequat chloride (CCC) [(500 and 1000) mg·L–1], or paclobutrazol (PBZ) [(500 and 1000) mg·L–1]. Results and discussion. Most levels of plant growth regulators significantly enhanced seedling growth. However, GA3 alone was most effective on stem height, leaf area, and shoot fresh and dry weights of both almond species. The thickest stems of P. amygdalus and P. webbii were obtained from the application of 100 mg GA3·L–1 followed by application of (1000 and 500) mg PBZ·L–1, respectively. In both species, PBZ significantly increased leaf chlorophyll content compared with the controls as well as with the other treatments. Application of GA3 alone on P. webbii and of GA3 followed by 100 mg ethephon·L–1 on P. amygdalus showed the highest root number, and root fresh and dry weights. High levels of soluble sugars and starch in the shoots and roots of both species were observed when GA3 application was followed by PBZ. Conclusion. These results demonstrated that application of plant growth regulators to the seedlings might be a useful way of enhancing growth of P. amygdalus and P. webbii and reducing the time and cost of seedling production.

Germination responses to water potential in neotropical pioneers suggest large-seeded species take more risks.

In neotropical forests, very small-seeded pioneer species (<0.1 mg seed mass) recruit preferentially in small tree fall gaps and at gap edges, but large-seeded pioneers do not. Since water availability is related to gap size, these differences in microsite preference may reflect in part species-specific differences in germination at reduced water potentials. For 14 neotropical pioneer species, the hypothesis is tested that small-seeded species, with shallow initial rooting depths, reduce the risks associated with desiccation by germinating more slowly and at higher water potentials than large-seeded species. Germination occurred both more quickly and at lower water potentials with increasing seed mass. For example, Ochroma pyramidale (seed mass 5.5 mg) had a time to 50 % germination (T50) of 2.8 d and a median base potential for germination (psi(b50)) of -1.8 MPa while Clidemia quinquenervia (seed mass 0.017 mg) had a T50 of 17.6 d and psi(b50) of -1.1 MPa. These data suggest that small-seeded species germinate only in comparatively moist microsites, such as small canopy gaps, which may reduce the risk of drought-induced mortality. Conversely, large-seeded species are able to germinate in the drier environment of large gaps, where they benefit by enhanced seedling growth in a high irradiance environment. The positive association of seed size and canopy gap size for optimal seedling establishment is maintained by differential germination responses to soil water availability coupled with the scaling of radicle growth rate and seed size, which collectively confer greater drought tolerance on large-seeded species.

Growth performance of some grasses in cattle dungpats in a greenhouse study

This study investigated the effects of dungpat thicknesses and water regimes on the emergence, shoot development, and survival of seedlings of bluebunch wheatgrass [ Psuedoroegneria spicata (Pursh) A. Love], Sandberg bluegrass ( Poa secunda L.), and Hycrest crested wheatgrass [ Agropyron desertorum (Fisch. Ex Link) Schult. X Agropyron cristatum (L.) Gaert.]. Pre-germinated seeds of each species were planted separately in the center and periphery of artificially prepared dungpats at heights of 0.5 cm for 1 cm-thick dungpats, 0.5 and 1.5 cm for 2 cm-thick dungpats, and 0.5, 2.0, and 3.5 cm for 4 cm-thick dungpats. In order to simulate natural drying conditions in the soil profile, half of the replications for each dungpat treatments received supplemental water, while the other half received no supplemental water during the study. Seedling emergence, development, and survival for all species were greatest when seeds were planted 0.5 cm from the bottom of dungpats and planted in 1 cm-thick dungpats. Supplemental watering enhanced seedling emergence and survival for all species. Hycrest crested wheatgrass had a greater seedling emergence than bluebunch wheatgrass and Sandberg bluegrass; and Hycrest crested wheatgrass and bluebunch wheatgrass had a greater seedling survival than for Sandberg bluegrass.

Arabidopsis cyclin D2 expressed in rice forms a functional cyclin-dependent kinase complex that enhances seedling growth

D-class cyclins play important roles in controlling the cell cycle in development and in response to external signals by forming the regulatory subunit of cyclin-dependent kinase (CDK) complexes. To evaluate the effects of D-class cyclins in transgenic rice plants, Arabidopsis cyclin D2 gene (CycD2) was linked to the maize ubiquitin1 promoter (Ubi1) and introduced into rice by the Agrobacterium-mediated transformation method. Genomic deoxyribonucleic acid (DNA), ribonucleic acid (RNA), and Western blot hybridizations of the Ubi1:CycD2 plants revealed copy number of transgene and its increased expression in leaf and callus cells at messenger RNA (mRNA) and/or protein levels. The H1 kinase assay using the immunoprecipitates of protein extracts from the Ubi1:CycD2 plants and nontransgenic controls demonstrated that the introduced Arabidopsis CycD2 forms a functional CycD2/CDK complex with an unidentified CDK of rice. Shoot and root growth was enhanced in the Ubi1:CycD2 seedlings compared with nontransgenic controls, together, suggesting that Arabidopsis cyclin D2 interacts with a rice cyclin-dependent kinase, consequently enhancing seedling growth.

Plant Emergence of PEG‐osmoprimed Seeds under Suboptimal Temperatures in Two Cultivars of Sweet Sorghum Differing in Seed Tannin Content

AbstractThe effect of polyethylene glycol (PEG) osmopriming on plant emergence in laboratory at optimal (25 °C) and suboptimal (18 and 14 °C) temperatures was assessed in two cultivars of sweet sorghum differing in kernel colour: Brandes, light‐coloured, and Roce, dark‐coloured. Sterilized sand or non‐sterilized soil were used as substrates. PEG osmopriming enhanced seedling emergence in sand. In soil, the light‐seeded cultivar produced seedlings only at optimum temperature, whereas the unprimed dark‐seeded cultivar performed well as in sand at all temperatures and reduced dramatically its germination capacity at suboptimal temperatures following priming treatment. These results might be related to the presence of tannins in the seed coat. Seed tannin contents of 80 and 590 mg 100 g−1 seed fresh weight (FW) were determined in Brandes and Roce respectively. These amounts consistently reduced after PEG osmopriming, especially in Roce (217.5 mg 100 g−1 seed FW). The decline in tannin content in Roce, because of osmopriming, might explain the poor emergence of this cultivar in soil. These results suggest the opportunity of using high‐tannin cultivars of sweet sorghum in the field, which may better growth in this environment when early sowings are required.

Use of Sodium Hypochlorite to Enhance Seedling Emergence, Vigor, and Survival of Angelica glauca and Aconitum heterophyllum

ABSTRACT Angelica glauca Edgew. and Aconitum heterophyllum Wall., high value, endangered medicinal plants of the Himalayan region, have low germination rates and slow seedling growth. The present study examined the effect of a common seed surface disinfectant, sodium hypochlorite (NaHClO3), on seedling emergence, vigor, and survival of the above species. Seeds of A. glauca soaked (treated) in NaHClO3 for 30 min and seeds of A. heterophyllum soaked in NaHClO3 for 15 min had resulted in increased and more uniform emergence, better survival, and more vigorous seedlings than control seedlings not treated with the NaHClO3. In A. heterophyllum, soaking periods exceeding 15 min inhibited seedling growth. A seedling size index that considered plant height, collar diameter, and root length was used to determine the most effective treatment for increasing seedling size in the selected species. The NaHClO3 treatment, which is inexpensive, easily available, and a simple procedure, should be highly useful, especially for poor and unskilled farmers, in developing large scale planting material for exsitu cultivation and thus conservation of these species.

Enhancing the Biological Control of Rice Seedling Disease by Adding Specific Carbon Sources into the Bacillus cereus D324 Formulation in Water-Seeded Rice

Utilization of carbon sources by Bacillus cereus D324, a biological control agent, and Pythium species, which causes rice seedling disease, was studied with the objective of increasing the efficacy of biological control by providing the biological control agent with specific beneficial carbon sources. D-galactose, D-sorbitol, and D-mannitol were poor carbon sources for Pythium spp. growth but were good for B. cereus D324 growth. Growth in a growth chamber of rice seeds coated with B. cereus D324 amended with specific carbon sources, such as D-galactose and D-sorbitol, showed significantly enhanced seedling emergence compared to seeds coated only with B. cereus D324. Field trials showed that both seedling emergence and yield increased, when the above specific carbon sources were added to B. cereus D324 in seed coating formulations. This result indicated that amending seed coating formulations with specific carbon sources could significantly increase seedling emergence and yield in the field.

Widespread mycorrhizal specificity correlates to mycorrhizal function in the neotropical, epiphytic orchid Ionopsis utricularioides (Orchidaceae)

Tropical orchids constitute the greater part of orchid diversity, but little is known about their obligate mycorrhizal relationships. The specificity of these interactions and associated fungal distributions could influence orchid distributions and diversity. We investigated the mycorrhizal specificity of the tropical epiphytic orchid Ionopsis utricularioides across an extensive geographical range. DNA ITS sequence variation was surveyed in both plants and mycorrhizal fungi. Phylogeographic relationships were estimated for the mycorrhizal fungi. Orchid functional outcomes were determined through in vitro seed germination and seedling growth with a broad phylogenetic representation of fungi. Most fungal isolates derived from one clade of Ceratobasidium (anamorphs assignable to Ceratorhiza), with 78% within a narrower phylogenetic group, clade B. No correlation was found between the distributions of orchid and fungal genotypes. All fungal isolates significantly enhanced seed germination, while fungi in clade B significantly enhanced seedling growth. These results show that I. utricularioides associates with a phylogenetically narrow, effective fungal clade over a broad distribution. This preference for a widespread mycorrhizae may partly explain the ample distribution and abundance of I. utricularioides and contrasts with local mycorrhizal diversification seen in some nonphotosynthetic orchids. Enhanced orchid function with a particular fungal subclade suggests mycorrhizal specificity can increase orchid fitness.

Facilitation and interference underlying the association between the woody invaders Pyracantha angustifolia and Ligustrum lucidum

AbstractQuestions: 1. Is there any post‐dispersal positive effect of the exotic shrub Pyracantha angustifolia on the success of Ligustrum lucidum seedlings, as compared to the effect of the native Condalia montana or the open herbaceous patches between shrubs? 2. Is the possible facilitation by Pyracantha and/or Condalia related to differential emergence, growth, or survival of Ligustrum seedlings under their canopies?Location: Córdoba, central Argentina.Methods: We designed three treatments, in which ten mature individuals of Pyracantha, ten of the dominant native shrub Condalia montana, and ten patches without shrub cover were involved. In each treatment we planted seeds and saplings of Ligustrum collected from nearby natural populations. Seedlings emerging from the planted seeds were harvested after one year to measure growth. Survival of the transplanted saplings was recorded every two month during a year. Half of the planted seeds and transplanted saplings were cage‐protected from rodents.Results: Ligustrum seedling emergence did not differ among treatments while growth was significantly higher in the absence of shrub cover. Sapling survival was significantly higher under the canopy of Pyracantha, intermediate under Condalia, and lowest in the absence of shrub cover. Caging did not affect growth but enhanced seedling emergence and sapling survival.Conclusion: The differential sapling survival in the shrub canopy treatments is consistent with natural sapling distribution. Pyracantha and, less so, Condalia, has a nurse‐plant effect on Ligustrum. This results from contrasting effects of the shrubs on different stages of the life cycle of Ligustrum: no effect on seedling emergence, negative on seedling growth, and positive on sapling survival. This suggests that efforts to control the expansion of Ligustrum over the landscape should tackle Pyracantha as well.

Fire season and intensity affect shrub recruitment in temperate sclerophyllous woodlands

The season in which a fire occurs may regulate plant seedling recruitment because of: (1) the interaction of season and intensity of fire and the temperature requirements for seed release, germination and growth; (2) post-fire rainfall and temperature patterns affecting germination; (3) the interaction of post-fire germination conditions and competition from surrounding vegetation; and (4) the interaction of post-fire germination conditions and seed predators and/or seedling herbivores. This study examined the effects of different fire intensities and fire seasons on the emergence and survival of shrubs representing a range of fire response syndromes from a summer rainfall cool climate region. Replicated experimental burns were conducted in two seasons (spring and autumn) in 2 consecutive years and fuel loads were increased to examine the effects of fire intensity (low intensity and moderate intensity). Post-fire watering treatments partitioned the effects of seasonal temperature from soil moisture. Higher intensity fires resulted in enhanced seedling emergence for hard-seeded species but rarely influenced survival. Spring fires enhanced seedling emergence across all functional groups. Reduced autumn recruitment was related to seasonal temperature inhibiting germination rather than a lack of soil moisture or competition. In Mediterranean-type climate regions, seedling emergence has been related to post-fire rainfall and exposure of seeds to seed predators. We think a similar model may operate in temperate summer rainfall regions where cold-induced dormancy over winter exposes seeds to predators for a longer time and subsequently results in recruitment failure. Our results support the theory that the effect of fire season is more predictable where there are strong seasonal patterns in climate. In this study seasonal temperature rather than rainfall appears to be more influential.

The creation of longitudinal cracks in shrinking soils to enhance seedling emergence. Part II. The effect of surface micro‐relief

AbstractCrusting and hardsetting phenomena are major problems in the emergence of delicate seedlings through weak structured soils. When a hard layer develops on the surface, it can retard seedling emergence and the trapped seedlings may perish unless the hard layer is broken or weakened. The development of natural desiccation cracks on the soil surface creates a route by which seedlings can emerge. The work conducted by the same authors suggested that the compaction of soil strips over the seed rows creates longitudinal cracks along the planting lines to improve seedling emergence. This study is an attempt to develop an alternative method to create the linear cracks using the effect of surface micro‐relief. Preliminary experiments showed that the creation of small furrows (50 mm deep) on the soil surface caused the appearance of cracks mainly at the bottom of the furrows. Monitoring the movement of aggregates during drainage, where small depressions are formed on the soil surface, revealed that the aggregates on either side of the turning point of the depression move in opposite directions as a result of the greater water tension developed in the ridges causing development of cracks at the turning point. Laboratory experiments indicated that the radius of curvature at the turning point of the depression, the spacing between depressions and the shape of ridges either side of the depressions are key factors influencing crack development at the bottom of depressions. A field experiment in semi‐arid central Iran confirmed the feasibility of the technique by the use of a backward raked shaper to develop small ridge and furrows on the surface of the seedbed which resulted in the creation of longitudinal cracks in the furrow bottoms, coincident with the seed row. An outline design of a press wheel is given.

Changes in germination percentages, protein and lipid contents of primed pepper seeds during storage

Pre-sowing seed treatments have been used in a large number of species to improve germination percentage and rate under adverse seedbed conditions, to enhance seedling emergence and to remedy the e...

The creation of longitudinal cracks in shrinking soils to enhance seedling emergence. Part I. The effect of soil structure

AbstractStand establishment in crusting soils is one of the most critical stages in the production of crops with delicate seedlings. This becomes more difficult in hard‐setting soils of arid lands where dispersion of aggregates due to irrigation results in the formation of a hard layer as the soil dries from the surface downwards and impedes seedling emergence. However, seeds planted near to natural cracks manage to emerge through them. The aim of this study was to improve seedling emergence of irrigated crops in arid and semi‐arid conditions by devising methods to create longitudinal cracks in the vicinity of the seed rows during the subsequent drying phase. Laboratory experiments were conducted in soil boxes containing air‐dried clay soils to investigate the influence of different mechanical effects on the cracking pattern after flooding. Promising results were achieved by compacting a 7–15‐mm wide strip along the seed row. Monitoring the effect of compaction on water release characteristics and tensile strength of soil revealed that the greater water loss of the surrounding non‐compacted soil caused a suction gradient towards the points of lower water content resulting in movement of water and particles towards the drier zones. The compacted soil with a greater tensile strength did not permit the flow of water and particles to the loose soil and a discontinuity occurred. A field experiment in central Iran proved the feasibility of the technique in a semi‐arid area. This was achieved by lightly compacting a narrow strip of soil by applying 17–35 kg on a 22‐mm wide, 558‐mm diameter wheel covered by a layer of flexible rubber which ran over the pre‐compacted soil.

The effects of natural and synthetic seed preconditioning agents (SPAs) in hastening seedling emergence and enhancing yield and quality of processing carrots

Field trials were conducted for two consecutive field seasons (2001 and 2002) to study the effects of various natural and synthetic seed preconditioning agents (SPAs) on seedling emergence as well as yield and recovery of carrots ( Daucus carota var. Sativus L.). Carrot seeds were preconditioned by soaking seeds in aqueous solutions containing various SPAs viz., Ambiol 0.1 mg L −1, glycinebetaine 100 mg L −1 (GB), BIOPROTECT 2 (BP2). Fields were located in Centreville (2001) and Medford (2002), King's County, Nova Scotia. Measurements were made on seedling emergence, soil moisture, soil temperature, final yield and recovery of various grades. Seed preconditioning using BP2 and GB during 2001 and BP2 and Ambiol during 2002 enhanced seedling emergence significantly and differentially in slicer and dicer varieties. Yield and recovery of fancy grade roots of Oranza increased nearly 71 and 146% respectively, compared to the untreated control during 2001 due to preconditioning using BP2. In a commercial scale field trial conducted in 2002, preconditioning with Ambiol (0.1 mg L −1) or GB (100 mg L −1) significantly enhanced emergence of dicer carrots by nearly four and three folds, respectively, over the untreated control. Final yield and quality however, was not increased by any of the SPAs in both slicer and dicer carrots in 2002. Preconditioning seeds using water was also equally effective as to that of SPAs in achieving early and high emergence suggesting the possibly of a natural SPA from carrot seeds. A significant enhancement in yield and root recovery due to BP2 preconditioning may perhaps be due to its enhanced sink activity facilitating root bulking together with its antistress, antioxidant properties protecting young seedlings from soil moisture deficits.

Capsule Treatments to Enhance Seedling Emergence of Gaura neomexicana ssp. coloradensis

Abstract Management of riparian vegetation is difficult because these communities are frequently impacted by herbivores, invasive weeds, and altered hydrologic regimes. Multiple and intertwined factors affecting rare species recruitment are particularly difficult to identify. Gaura neomexicana ssp. coloradensis Munz (Gaura) is a short‐lived perennial forb endemic to riparian areas in mixed‐grass prairies of Wyoming, Nebraska, and Colorado, U.S.A. It became a federally listed threatened species in October 2000. Because the species is a recruitment‐limited monocarpic perennial, we studied the effects of six capsule‐collection dates, a 2‐month cool‐moist stratification, 24‐hr leaching, and 24‐hr imbibition on Gaura seedling emergence. Seedling emergence did not vary with collection date. Capsules collected from Gaura plants grown at the Bridger Plant Materials Center in Montana exhibited greater emergence than capsules harvested from endemic populations near Cheyenne, Wyoming, suggesting that maternal plant growing conditions impact dormancy. Because cool‐moist stratification enhanced seedling emergence of Gaura and leaching did not, sufficient moisture during cool temperatures may be more critical than leaching of germination inhibitors as might occur with normal stream flows. Spring flooding may enhance Gaura recruitment by increasing the availability of riparian sites that are inundated during periods of cool temperatures. If so, hydrologic and climatic regimes must be considered in restoring the unique conditions needed for germination of this rare riparian endemic.